Copyright 2010 Fox Searchlight Pictures. All rights reserved.Although they're very different films, the movies Black Swan and Limitless share a common theme: They're both about the radical transformation of their lead characters. They also share a common trait: Both feature extremely creative--and often subtle--visual effects to showcase that transformation.

A few weeks back, we spoke with Comen VFX visual effects supervisor Tim Carras and visual effects producer Josh Comen about how the "infinite zoom" sequence in Limitless came together. Carras and Comen worked on weaving together and compositing the continuous shot, which was filmed with a three-camera rig that remained static--even though the sequence itself never stops moving.

In an IFC.com interview, Limitless director Neil Burger mentioned Look Effects visual effects supervisor Dan Schrecker as the idea man behind the three-camera rig used for the "infinite zoom" sequence. We spoke to Schrecker about the story behind the rig, about other memorable visuals in Limitless, and about his work on the extensive effects in Black Swan.

Video Copyright 2010 Fox Searchlight Pictures. All rights reserved.

PCWorld: How did you get involved with Limitless?

Dan Schrecker: I actually met with Neil [Burger] probably about three and a half years ago, when he was doing the project with Shia LeBoeuf, who broke his hand on Transformers, and the project fell apart. We had a good meeting and it was pretty cool, but nothing really happened. And then cut to a few years later--I dropped an e-mail to Scott Kroopf, the producer, to say, "Hey, I see you guys are doing this, and I work for this company Look Effects now, and I'd love to be involved." I also know Chris Scollard, who was the on-set effects supervisor, so I talked to him. Eventually they got into post-production, and they had these effects that they'd shot but hadn't quite figured out before they shot.

They'd shot a lot of the film's effects another way, but it just didn't add up to what Neil wanted. So he needed a lot of concept design in post, and I sort of kept pestering them, and I caught them on the right day, where it was just perfect timing.

We eventually got awarded a big chunk of all the NZT effects. In addition to these fractal zooms, there was this 360-degree shot, and a number of other ones that were conceptual stuff that hadn't been figured out. In some ways, Neil's ideas hadn't changed, they just weren't quite fully realized during principal photography.

PCW: What were some of the issues with the initial shots?

Dan Schrecker: There were shots during principal production where they did these different "moves" down the street. It didn't quite work, and there was no real way to do actual camera movement without motion control and multiple locations. I came on in the post-production process, and we came up with this idea that if there was a high enough resolution image, we could push in and create our own zoom without moving the cameras, and control the speed of the zoom.

What we ended up doing is that we had three Red cameras mounted on the same tripod with different focal lengths. We'd take the tripod, go set it up on a corner, set up the tableau or whatever the action was, and then shoot it simultaneously with the three cameras. We'd take the footage from the longest lens and embed it inside the footage from the shortest and middle lens, so you have this image with more resolution in the center. That way, when you push in, the image doesn't break apart.

Once this idea sort of popped into my head, it was like, "that's going to be the way to do this." We tested it first with some stills, did some initial tests outside our office in Brooklyn, and showed those to Neil. It solved all the problems, because we controlled the speed. One of the difficulties we had on some of the [principal] shots was trying to match up camera movement to other things in the scene. This way, we controlled everything, which is ultimately what we needed.

It was fairly easy to set up because it was just putting the cameras on the sticks. And then Neil had the freedom to do whatever he wanted with the scene, and we figured a lot of it out in post. And everyone in that fractal-zoom scene is an extra. We set them up in different places, and in some places Neil wanted them to look at the camera. In another part we had a Bradley Cooper double run away from the camera, and different things like that.

PCW: Once that footage was shot, was it smooth sailing, or did other issues pop up?

Dan Schrecker: One of the issues was just nodal offset on the cameras. All the cameras are on the same tripod, but they're still 6 or 7 inches apart, which is the width of the Red body. So that was something we had to compensate for--how these images were embedded in one another got a little tricky and had to be cleaned up. If you take one of the images and place it into another without really finessing it, you're going to see that rectangle of the smaller image. The perspective's just off enough that you've got to pick and choose where your scenes start and end. We constructed these shots and walked around with Neil, picking POVs that had interesting architecture, and decided, "that's where our scene is until we get to that awning"--and after that plate, after that awning, will be location number two.

PCW: When anyone in the film takes the NZT drug, the visual style turns into a 360-degree effect, as you mentioned. Did you use a special lens for those shots, or was that effect done in post-production?

Dan Schrecker: What they did in production was, they had three fish-eye lenses on a rig. The rig was on a Steadycam so that they could move the camera, but the three fish-eye lenses didn't give you full coverage, so you had blind spots between the lenses. You did have 360, but minus 15 degrees in the middle. So it didn't work, for the most part. There are, I think, three of the 360-degree shots in the film, and they all sort of had to be rethought.

In the first scene with that effect, the first time he takes the drug, they're in the hallway where he's talking to the landlady. For that one, we ended up reshooting the actress, T.V. Carpio, on a green screen with a camera dolly. We start tight on her face and then widen out. In [principal photography], the stairwell was actually a set they'd built and destroyed, so we had to go into these fish-eye angles and basically pull out frames at certain points and re-create a matte painting.

We built a matte painting out of the hallway, and then we worked with Neil to figure out the level of distortion and how the distortion changes in the shot. Once we had the green screen and the matte painting built, it flowed pretty easily for that one. We wanted it to start out looking normal on T.V.'s closeup, and then as it pulls back, it sort of sucks in from the side, and Neil was very specific about how he wanted these edges to push in from the side.

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One of the solutions we came up with for reshooting the other scenes was that we got a panoramic photo bowl, which is basically a mirrored half-ball that sits on the lens, and you point the lens up; it shoots into the ball, and you have a full 360. The problem with that was the resolution, because the optics on that mirror weren't quite good enough. We shot it with a Red because the bowl wouldn't fit onto a 35mm camera, since it's made for an SLR camera.

The one in Central Park, we shot it with this 360 lens, and it just didn't work, so we ended up shooting a bunch of plates of Central Park that we tiled together. And that one was actually the 360 effect combined with the fractal-zoom effect. As Lindy takes the drug, she's looking at this rock, and it pulls out to a full 360, and then it pushes in to these different things that Lindy sees around her that she can use as a weapon. We combined all that into this one shot, which was cool.

There's also this scene on Fifth Avenue where Eddie's taking the drug, and he's walking down the street. That was one they shot with the three-lens setup. But again, we'd have these dead spots where people would walk by the camera and would disappear for an instant before they reappeared in the next one.

The issue was how to reshoot it. It's one thing to set up our tripod with the 360 lens and the wraparound thing, but how do we do a moving one that isn't bumpy? What we ended up doing was getting a little person to hold the camera, because it had to be at a certain height. He held a Red with the mirror ball and walked down the street so we'd have that effect. But again, the resolution wasn't good enough, and we couldn't use it.

So they ended up keeping the original shot. If you look at the Fifth Avenue 360 shot in the movie, you'll see these blind spots as people walk in and out of the fish-eye lens.

PCW: You also worked on the effects for Black Swan. And you've worked on every Darren Aronofsky film?

Yeah, we went to school together. We're old friends.

PCW: For Black Swan, can you talk about the process behind the scene where Natalie Portman morphed into a swan?

Dan Schrecker: For those scenes, it was a full-body dance double doing the dance with motion capture. So we captured her movement, and Natalie did a pass of the same scene for her head. The wings are all computer-generated, and we CG'd in the crowd.

[Autodesk] Maya was our primary 3D-animation package for the black-swan transformation. We did a combination of modeled feathers for the primary and secondary feathers, rigs, [Maya] MEL scripts, lighting effects, and Mental Ray [rendering software].

PCW: The film also has a lot of scenes where the camera is looking directly into a mirror, and you never see a reflection of the camera crew.

Dan Schrecker: Yeah, there was a lot of crew removal throughout the whole thing. There's mirrors everywhere in that movie. To do that, you have to get a clean plate [for the reflected scene]. So you shoot the shot, and then you turn around and shoot the other direction. We added what's back there, reflected in the mirror, with [rotoscoping].

PCW: The dance sequences in Black Swan and the face-replacement effects are a controversial topic right now. Did the dancers have to wear some sort of green-screen mask for the face-replacement effects to work?

Dan Schrecker: No, nothing like that. What we did for the face-replacement stuff ... basically the dance double would do the dance, Natalie would come out and do the exact same dance in the exact same lighting with the same camera movement, and it was just a cut-and-paste.

It was a small percentage of the dancing scenes, maybe 10 or 15 percent. We didn't do it too much. The whole thing sort of annoyed me, the controversy. We also did face replacements to illustrate Nina's breakdown ... she's leaving the stage as the white swan, and the ballet dancers all have her face.